In social software systems there are often discussions, where the participants are seeking experts' assistance. It can be an on-line meeting, an email thread, a forum discussion or a thread of comments on some document like a wiki page or a blog. When there are unresolved issues, or the parties cannot agree on the correctness of their assumptions, usually one of the participants asks his colleague, who is an expert in the discussed field to step in and help.
Even when such an expert is added to the discussion and expresses his opinion, his opinion is not always acceptable for all the parties. In particular because the expert is not always known to all the parties, or because he might not be considered an expert by all the parties. Another scenario is when the parties find an expert by searching in the system, and then if the expert doesn't know them personally then he might be reluctant to help.